[Elecraft] K2 Audio mod comment

[Roelof Bakker]

Hello All,

Matti, TF3MA has suggested a mod for the K2 to improve the low frequency 
audio response by increasing the value of C25 and C26. Matti used 100 nF / 
0.1 uF in parrallel to C25 and C26. I had some 470 nF / 0.47 uF smd (1206) 
capacitors available and soldered  these at the bottom side of the control 
board PCB. This is a very easy mod and only requires one to remove the top 
cover and uninstalling the control board.

As a result it is now a joy to listen at a low pitch in CW mode.

Thanks!

Roelof Bakker, pa0rdt


TF3MA wrote:

But I discovered that my K2, had a rather limited low freq audio
response. So I took a look at the schematic for the audio circuit in the
K2...

The original low freq. cutoff (-3db) freq. is approx. 640Hz (with KAF or
DSP moduls installed) or 400Hz (with no audio moduls) determined by C25,
C26 and the 5kOhm volume control (and NE612 mixer impedance), to extend
the audio frequency response for the low freq. I put
0.1uF SMD across C25 and C26, extending the low frequency response to
approx. 320Hz. This improves the SSB sound of the receiver, and improves
SNR when copying low pitch CW signals. This simple mod increases the rx
audio signal at 300 Hz by about 3dB. 


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